To the surface of a conventional medical tool having a portion to come in contact with a living body, a coating layer exhibiting lubricity in wet conditions has been applied by various techniques in order to reduce pains or damage to a living body due to the resistance at the time of contact. However, the conventional coating layer typically has a low affinity with materials constituting medical tools and unfortunately may be eluted or exfoliated in a living body.
The technique for overcoming such disadvantages is exemplified by the method that is disclosed in Patent Document 1 and includes ozone treatment of the surface of an object composed of a polymer material to form a functional group on the surface and graft polymerization of a hydrophilic polymer to the functional group and the method that is disclosed in Patent Document 2 and includes plasma treatment of the surface of an object. These methods however have problems of poor durability of the hydrophilic polymer and a reduction in mechanical properties of the object and are not preferred.
Patent Document 3 discloses a method of forming a coating layer having an interpenetrating network structure of a first polymer compound and a second polymer compound on the surface of an object by polymerizing a monomer in the presence of the first polymer compound having hydrophilicity to form the second polymer compound. The method however has problems of deterioration of the object and elution of residual monomers and oligomers.
Patent Document 4 discloses a method of forming a coating layer by using a urethane resin having a hydrophilic skeleton. The method prevents mechanical properties of an object from deteriorating but has problems of insufficient adhesiveness of the coating layer with an object and insufficient lubricity in wet conditions.
Patent Document 5 discloses a method of forming a coating layer by using a hydrophilic polyurethane having a block isocyanate with a terminal isocyanate group protected by a protective group. The method can solve the problems of Patent Document 4, however, has safety issues because a catalyst such as an amine and a heavy metal including tin is required to be used in order to form a urethane bond on an object. In addition, the method necessitates an increase in temperature, and this may affect the mechanical properties of an object or the profile of a medical tool. The method thus involves new problems to be solved.
Patent Document 6 discloses a method of forming a hydrophilic urethane coating layer by reacting a urethane compound containing a hydrophilic ethylene oxide on the surface of an object. In the method, the reaction rate is insufficient, and thus unreacted isocyanate is likely to cause the adhesion of the coating layers to each other or the adhesion between the coating layer and a package. In order to prevent the adhesion, heating or curing for a long period of time is required, but such treatment is undesirable from the viewpoint of the effect on the performance of an object and productivity. Use of a reaction catalyst in order to suppress the effect on the performance of an object or the reduction in productivity causes a problem of affecting biological safety.
Patent Document 7 discloses a method of bonding a coating layer composed of a maleic anhydride copolymer to the surface of a resin object through covalent bonds. In the method, a coating solution containing a maleic anhydride copolymer is applied to the surface of a resin object, and then the coating is required to be treated at a high temperature of 101 to 220° C. for a long period of time. This causes problems of the deterioration of mechanical properties of an object and of affecting the profile of a medical tool due to thermal degradation, for example.
Patent Document 8 discloses a method of forming a coating layer composed of a mixture of a maleic anhydride polymer substance and polyurethane having an allophanate bond on the surface of a resin object. The method uses a decomposition reaction of the allophanate bond of the polyurethane to crosslink the polyurethane with the maleic anhydride polymer substance, thus necessitates the treatment at a high temperature of 120 to 140° C., and has a problem of the deterioration of mechanical properties of an object.
Patent Document 9 discloses a coating solution for forming a coating exhibiting lubricity in wet conditions on the surface of a medical tool. The coating solution contains a hydrophilic polymer exhibiting lubricity in wet conditions, such as polyurethane, and a binder copolymer having a vinyl moiety and a carboxylic acid moiety. According to Example C-1 in Patent Document 9, the coating exhibiting lubricity in wet conditions prepared by using a vinyl ether/maleic anhydride copolymer (trade name: Gantrez (trademark) AN119) as the binder copolymer has insufficient durability against abrasion.
Patent Document 10 discloses a coating solution for forming a coating exhibiting lubricity in wet conditions on the surface of a medical tool. The coating solution is prepared by dissolving a methyl vinyl ether/maleic anhydride copolymer, a thermoplastic polyurethane (trade name: Tecoflex) synthesized by using an aliphatic isocyanate as a raw material, and a polyol such as polypropylene glycol as a crosslinking agent in an organic solvent such as tetrahydrofuran. However, the coating solution is required to be stored at 20° C. or less before application to the surface of a medical tool. It is thus supposed that each component contained in the coating solution has very high reactivity and a reaction product of the components has insufficient adhesiveness with the surface of a medical tool, for example.